General Circulation and Its Impact over the Northern Hemisphere in 1999

General circulation features over the Northern Hemisphere in 1999 were analysed.It is shown that the 500hPa subtropical high over the west Pacific was weaker than that of last year.Its ridge point is anomaly to the east in spring and summer.At 500hPa,zonal and meridional circulation take place by turn,cold air is weaker than normal in winter.Monsoon is stronger during summer.The convection activity is strong during winter and spring,and it is weaker in tropics in summer.A strange La-Nina event is persisting in the tropical Pacific region in 1999.The anomaly of both the tropical Pacific and atmosphere circulation exerted a significant impact on weather and climate in China.

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